CN115263264B - Efficient extraction method for gas coordination of close-range coal seam group mining layer and adjacent layer - Google Patents
Efficient extraction method for gas coordination of close-range coal seam group mining layer and adjacent layer Download PDFInfo
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- CN115263264B CN115263264B CN202210930029.4A CN202210930029A CN115263264B CN 115263264 B CN115263264 B CN 115263264B CN 202210930029 A CN202210930029 A CN 202210930029A CN 115263264 B CN115263264 B CN 115263264B
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- 239000003245 coal Substances 0.000 title claims abstract description 153
- 238000000605 extraction Methods 0.000 title claims abstract description 57
- 238000005065 mining Methods 0.000 title claims abstract description 41
- 238000005553 drilling Methods 0.000 claims abstract description 48
- 238000000034 method Methods 0.000 claims abstract description 22
- 238000004519 manufacturing process Methods 0.000 claims abstract description 9
- 238000010276 construction Methods 0.000 claims description 31
- 239000011435 rock Substances 0.000 claims description 23
- 238000004364 calculation method Methods 0.000 claims description 9
- 238000005265 energy consumption Methods 0.000 claims description 4
- 230000002265 prevention Effects 0.000 abstract description 7
- 238000011161 development Methods 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 abstract description 4
- 239000010410 layer Substances 0.000 description 110
- 238000010586 diagram Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000011241 protective layer Substances 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/14—Obtaining from a multiple-zone well
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimizing the spacing of wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
Abstract
The invention relates to a close-range coal seam group mining layer and adjacent layer gas coordination efficient extraction method, and belongs to the field of prevention and treatment of coal mine and gas outburst. The method comprises the following steps: s1: arranging directional long drilling holes and comb-shaped branch holes; s2: calculating the parameters of the directional long drilling and comb-shaped branches Kong Shigong; s3: constructing a directional long drilling hole and a comb-shaped branch hole; s4: staged hydraulic fracturing of a first production layer and a passing coal layer; s5: and (5) coordinating and efficiently extracting gas in the mining layer and the adjacent layers. The invention adopts the directional long drilling and comb-shaped branch hole subsection hydraulic fracturing technology by utilizing the development roadway before coal seam exploitation, realizes the efficient extraction of gas coordination of the exploitation layer and the adjacent layer in the exploitation layer exploitation process, reduces the gas hazard from the source, and has important significance for preventing the coal seam and the gas overrun accident from being uncovered by a close-range coal seam group, reducing the extraction engineering quantity and the cost, improving the gas extraction efficiency, and realizing the efficient extraction and the efficient outburst prevention.
Description
Technical Field
The invention belongs to the field of prevention and control of coal mine and gas outburst, and relates to a close-range coal seam group mining layer and adjacent layer gas coordination efficient extraction method.
Background
The disaster of outburst of coal mine and gas (simply called outburst) seriously affects the safe production of the coal mine. As is well known, protective layer mining is widely used as an important means for outburst prevention, but part of coal seams are short-distance coal seam groups, the interlayer spacing between the coal seams is smaller than 20m, and the interlayer spacing between the coal seams is only 3-5 m, so that the protective layer mining conditions are not met, and accidents such as mistaken uncovering of the coal seams and gas overrun easily occur due to the influence of adjacent layers in the mining process of a certain coal seam. Secondly, the outburst prevention and gas overrun prevention and control of the exploitation layers and adjacent layers which are close to each other at present mainly utilize spatial relations to arrange a plurality of coals, rock roadways (such as 6 roadways are arranged on one working surface of a Huainan mining area) and a plurality of extraction holes (sequential layer drilling, layer penetrating drilling, directional long drilling and the like) for gas extraction, and the methods play a certain role, but have the problems of high extraction engineering quantity, high cost, high extraction difficulty, low deformation and collapse of the drilling and the like, and severely restrict the safe and efficient production of the coal mine.
Disclosure of Invention
In view of the problems that accidents are easy to occur in a close-range coal seam group, the extraction engineering amount is high, the extraction difficulty is high, the efficiency is low, and the like, the directional long drilling is combined with the comb-shaped branch hole subsection hydraulic fracturing technology, the gas coordination efficient extraction of the extraction layer and the adjacent layer is realized in the extraction process of the extraction layer, the gas hazard is reduced from the source (namely, the advanced and efficient extraction of gas by using a development roadway is realized before the coal seam extraction), the mistaken coal seam uncovering and gas overrun accidents are prevented for the close-range coal seam group, the extraction engineering amount and the extraction cost are reduced, and the important significance is provided for improving the gas extraction efficiency, the efficient extraction and the efficient outburst prevention.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a close-range coal seam group mining layer and adjacent layer gas coordination efficient extraction method comprises the following steps:
s1: arranging directional long drilling holes and comb-shaped branch holes;
s2: calculating the parameters of the directional long drilling and comb-shaped branches Kong Shigong;
s3: constructing a directional long drilling hole and a comb-shaped branch hole;
s4: staged hydraulic fracturing of a first production layer and a passing coal layer;
s5: and (5) coordinating and efficiently extracting gas in the mining layer and the adjacent layers.
Further, in step S1, the directional long drill holes are arranged in an upper hard rock stratum of a roof fracture zone of a shallowest part of the coal seam of the same group of short-distance coal seams.
Further, in step S1, the comb-shaped branch hole has an obvious guiding function, and has a function of simultaneously and efficiently extracting gas from the mining layer and the adjacent layer, and the final position of the comb-shaped branch hole is arranged at the rock stratum 1m below the bottom plate of the first mining layer.
Further, in step S2, comb branch Kong Shigong parameters are calculated, expressed as:
X n ＝Y n ＝(X 1 2 ÷K n1 ) 0.5 ×K y ÷i 0.5
wherein X is n 、Y n The construction distance and the inclined construction row distance of the comb-shaped branch holes of the nth layer of coal bed are respectively the construction distance and the inclined fracturing range of the nth layer of coal bed; x is X 1 K is the hydraulic fracturing range of single coal seam trend n1 The thickness influence coefficient of the comb-shaped branch hole coal bed for the n layers of coal beds; k (K) y Is the rock mass energy consumption coefficient; i is comb shape between primary hydraulic fracturing sectionsThe number of branch holes.
Further, in step S2, the coal seam thickness influence coefficient K of the comb-shaped branch hole n1 The calculation formula of (2) is as follows:
K n1 ＝Z n /Z 1 ＝(X 1 *Y 1 )/(X n *Y n *i)＝X 1 2 /(X n 2 *i)
wherein Z is 1 、Z n The sum of the coal seam thicknesses of the single coal seam, the 1 st layer and the n th layer coal seam is respectively Y 1 Is a single coal seam prone hydraulic fracturing range.
Further, in step S2, the directional long drilling tendency construction pitch is the same as the comb-shaped branch hole tendency construction pitch.
Further, the step S4 specifically includes: and the hydraulic fracturing is carried out on the first mining layer and a plurality of comb-shaped branch holes passing through the coal bed, so that the air permeability of the mining coal bed and the air permeability of the passing through coal bed are increased.
Further, in step S5, when mining the shallowest part of the same group of close-distance coal seam groups, it is possible to realize the coordination of efficient pre-extraction of mining layer gas and pressure relief of extracting all the underlying adjacent layer gas. When the deepest part coal seam of the same group of close-range coal seam groups is mined, the coordination of high-efficiency pre-extraction of mining layer gas and pressure relief extraction of all overlying adjacent layer gas can be realized. When coal beds between the shallowest part and the deepest part of the same group of close-range coal beds are mined, the efficient pre-extraction of gas in the mining layer and the pressure relief extraction of gas in all the lower adjacent layers and the upper adjacent layers can be coordinated.
The invention has the beneficial effects that: the invention reduces the gas hazard from the source, adopts the directional long drilling and comb-shaped branch hole sectional hydraulic fracturing technology by utilizing the development roadway before the coal seam exploitation, and realizes the efficient extraction of the gas coordination of the exploitation layer and the adjacent layer in the exploitation layer exploitation process; the method has important significance for preventing coal bed and gas overrun accidents from being uncovered by mistake, reducing the extraction engineering quantity and cost, improving the gas extraction efficiency, and preventing outburst in high efficiency.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.
Drawings
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:
FIG. 1 is a flow chart of a method for efficiently extracting gas from a near-distance coal seam group mining layer and an adjacent layer in a coordinated manner;
FIG. 2 is a schematic plan view of the directional long drilling and comb-shaped branch hole construction parameters calculation;
FIG. 3 is a schematic view of a directional long borehole and comb-shaped branch hole construction parameter calculation section;
FIG. 4 is a schematic diagram of a hydraulic fracturing process with a first production layer being layer 2;
FIG. 5 is a schematic diagram of a directional long borehole and comb-shaped branch hole arrangement for a first production layer 1;
FIG. 6 is a schematic diagram of an arrangement of directional long boreholes and comb-shaped branch holes with an nth layer as a first production layer.
Reference numerals: 1 is directional long drilling, 2 is comb-shaped branch hole, 3 is coal seam, 4 is development of up-down mountain roadway, 5 is hydraulic fracturing pump set, 6 is front end packer, 7 is rear end packer, 8 is goaf, and 9 is fracture zone (produced after exploitation).
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.
Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.
Referring to fig. 1, the invention provides a method for efficiently extracting gas from a close-range coal seam group mining layer and an adjacent layer, which specifically comprises the following steps:
step 1: directional long drilling holes and comb-shaped branch holes are arranged.
(1) And determining the directional long drilling construction horizon.
And collecting a comprehensive mine histogram, mine geological drilling and constructed drilling, analyzing lithology and mechanical parameters of the top plate rock stratum of the shallowest part of the close-range coal seam group, and determining a reasonable construction horizon of the directional long drilling of the top plate of the shallowest part of the coal seam along the vertical direction of the coal seam by combining the performance of a directional drilling tool of the directional drilling machine.
In order to ensure that the directional long drilling holes are always used in the exploitation process of each coal seam of the coal seam group, according to the theory of three zones of a top plate, the directional long drilling holes are arranged in an upper hard rock stratum of a roof fracture zone, and the theory of three zones can be specifically referred.
(2) The comb finger Kong Zhongkong position is determined.
The comb-shaped branch holes have obvious guiding function and have the function of simultaneously and efficiently extracting gas from the mining layer and the adjacent layer, and the final position of the comb-shaped branch holes is arranged at the rock stratum 1m below the bottom plate of the first mining layer.
Step 2: the directional long borehole and comb branch Kong Shigong parameters are calculated.
(1) Comb finger Kong Shigong parameters are determined.
According to the existing research, the hydraulic fracturing parameters are mainly related to the thickness of coal seams and the conditions of rock formations between coal seams. Therefore, the hydraulic fracturing construction parameters of the multiple coal beds can be determined by analyzing the coal bed thicknesses and the rock stratum conditions between the single coal bed and the multiple coal beds.
Referring to fig. 2 and 3, taking first mining layer 2 coal seam as an example, assume that the construction pitch of any single coal seam segmented hydraulic fracturing in the coal seam trend direction is known to be X 1 Construction distance Y in direction of inclination 1 First, the layer 2 coal seam is mined, namely the layer 1 and the layer 2 coal seam are simultaneously hydraulically fractured. Then, the comb-shaped branch hole is segmented, the hydraulic fracturing is performed on the construction row spacing X in the coal seam trend direction 2 Construction distance Y in direction of inclination 2 The calculation method of (2) is described in detail as follows:
1) Analysis of coal seam thickness influence coefficient
Assuming that the thickness of any coal seam is known to be Z 1 The trend and the fracturing trend range are respectively X 1 、Y 1 The volume of the fracturing coal body of the hydraulic fracturing pump set is as follows:
V 1 ＝X 1 *Y 1 *Z 1 (1)
according to the law of conservation of energy, the volumes of the coal bodies which are fractured by the same hydraulic fracturing pump set are equal, namely the volumes V of the coal bodies of the single coal bed which are fractured by the same hydraulic fracturing pump station 1 And the volume V of the coal body for fracturing the 1 st layer and the 2 nd layer coal layers 2 Should be equal, the following calculation formula can be obtained:
V 2 ＝V 1 ＝X 1 *Y 1 *Z 1 ＝X 2 *Y 2 *Z 2 *i (2)
wherein X is 1 、Y 1 The trend of a single coal bed and the range of the inclined hydraulic fracturing are respectively m; x is X 2 、Y 2 The trend and the fracturing trend range of the layer 2 coal bed and m are respectively; z is Z 1 、Z 2 The sum of the coal seam thicknesses of the single coal seam, the 1 st layer and the 2 nd layer coal seam is m; and i is the number of comb-shaped branch holes between the primary hydraulic fracturing sections.
Here, the coal bed is simplified into isotropic homogeneous material, and then the single coal bed has a trend and a fracturing trend range X 1 、Y 1 The trend and the fracturing trend range X of the 1 st layer coal bed and the 2 nd layer coal bed are equal in size 2 、Y 2 Equally, the overall fracturing of the 1 st and 2 nd coal layers is equivalent to only a single coal layer increasing the thickness of the coal layer, where the ratio K of the thicknesses of the 1 st and 2 nd coal layers and the single coal layer is defined 21 The method is characterized in that the method is used for realizing the coal seam thickness influence coefficient in the hydraulic fracturing range of two layers of coal, and meanwhile, parallel hydraulic fracturing of comb-shaped branch holes is considered. Then, the calculation formula of the coal seam thickness influence coefficient in the hydraulic fracturing range is as follows:
K 21 ＝Z 2 /Z 1 ＝(X1*Y 1 )/(X 2 *Y 2 *i)＝X 1 2 /(X 2 2 *i) (3)
2) Rock energy consumption coefficient analysis
Because the hardness of the rock stratum is far greater than that of the coal seam, hydraulic fracturing energy mainly acts on the weak coal body, and a small part of energy is consumed on the rock body due to friction, wherein the ratio of the energy consumed by the rock body to the fracturing energy is defined as a rock energy consumption coefficient Ky, the coefficient can be obtained through on-site investigation, and the empirical value is generally 0.1-0.3.
3) Construction parameter determination
Deducing according to the formula (3) to obtain the construction distance X of the comb-shaped branch holes of the coal seam of the 1 st layer and the coal seam of the 2 nd layer 2 Inclined construction row spacing Y 2 The method comprises the following steps:
X 2 ＝Y 2 ＝(X 1 2 ÷K 21 ) 0.5 ×K y ÷i 0.5 (4)
the calculation method of the strike construction distance and the inclined construction row distance of other coal beds is the same as the calculation method.
(2) Determining directional long drilling construction parameters
Obviously, the directional long drilling tendency construction row distance is the same as the comb-shaped branch hole tendency construction row distance, and the drilling length of the directional long drilling is generally the same as the length of a stope face and is generally 500-1000 m.
Step 3: and constructing directional long drilling holes and comb-shaped branch holes.
Taking the first mining of the layer 2 coal seam as an example, referring to fig. 2 and 3, the construction is performed according to the directional long drilling and comb-shaped branch hole construction parameters determined in the step 2, and the main construction process is as follows:
the directional drilling adopts a secondary hole body structure, the primary hole is drilled by a rotary drill, and the hole drilling tool assembly is a phi 98mmPDC drill bit plus a phi 73mm common rotary drill rod; the primary reaming drilling assembly is a phi 96 mm/phi 153mm PDC combined drill bit, a special centralizer and a phi 73mm common rotary drill rod; the secondary reaming drilling assembly is a phi 153 mm/phi 193mm PDC drill bit, a special centralizer and a phi 73mm ordinary rotary drill rod, and a phi 146mm sleeve is put into the secondary reaming drilling assembly for 60m after reaming is completed. The secondary hole adopts directional drilling, and the drilling tool combination is a phi 98mmPDC drill bit, a phi 73mm hole bottom motor, a non-magnetic drill rod under phi 73mm, a measurement while drilling instrument, a non-magnetic drill rod on phi 73mm and a phi 73mm center cable drill rod.
The comb-shaped branch hole construction adopts an advancing branch hole technology, namely, branch holes are opened from the orifice to the bottom of the hole, namely, the branch hole construction is carried out while the main hole is drilled, and the used drill bit, drill rod and directional long drilling hole are the same.
Step 4: staged hydraulic fracturing of the first production zone and the passing coal bed.
Taking the first coal seam of layer 2 as an example, please refer to fig. 4, in order to ensure the effectiveness of hydraulic fracturing drilling hole sealing, and ensure the smooth implementation of the hydraulic fracturing process, a sleeve+packer hole sealing mode is adopted. The directional drilling hydraulic fracturing mode is backward type sectional fracturing, namely hydraulic fracturing is sequentially carried out from the bottom of the hole to the direction of the hole. And assuming that the number of comb-shaped branch holes of each fracturing section is i, namely respectively installing a sleeve and a packer at the position 1m in front of the 1 st branch hole and at the position 1m behind the i st comb-shaped branch hole to perform hydraulic fracturing, and then completing the working procedures of pressure maintaining, water draining and the like according to requirements. And (3) carrying out hydraulic fracturing on other hydraulic fracturing sections of the directional long drilled hole section by adopting the same method until all branch holes are subjected to hydraulic fracturing.
Step 5: and (5) coordinating and efficiently extracting gas in the mining layer and the adjacent layers.
And (3) connecting the directional long drill holes of the coal seam with a drainage pipeline to conduct gas drainage, and independently installing a drainage metering device to conduct gas drainage metering, wherein after the drainage of the first drainage layer reaches the standard, the first drainage layer can be subjected to the mining activity, and the efficient drainage of the mining layer and the gas of the adjacent layers are coordinated in the coal seam mining process.
Example 1: referring to fig. 5, if the 1 st layer of coal seam is mined first, the final position of the comb-shaped branch holes falls to the 1m position of the bottom plate of the coal seam 1. As can be seen from fig. 5, the coal seam is first hydraulically fractured by using the directional long drilled holes and the comb-shaped branch holes, and then gas extraction is performed on the extraction layer (layer 1 coal seam) after hydraulic fracturing, and the extraction operation is performed on the layer 1 coal seam after the gas extraction reaches the standard. In the mining operation process, the coal seam of the coal seam roof and the floor and the rock stratum are all affected by mining to form a goaf 8, the pressure of the coal seam roof and the floor and the rock stratum can be relieved, a fracture zone 9 can be generated, and the constructed directional long drilling holes and comb-shaped branch holes can be used for extracting pressure relief gas of the lower adjacent layers (the 2 nd layer to the n layer of coal seam). The coordinated efficient extraction of the exploitation layer (the 1 st layer of coal seam) and the underlying adjacent layers (the 2 nd layer to the n layer of coal seam) is realized.
Example 2: referring to fig. 4, if the layer 2 coal seam is mined first, the comb-shaped branch hole end positions are arranged at the bottom plate of the coal seam 2, see rock 1 m. As can be seen from fig. 4, the coal seam is first hydraulically fractured by using the directional long drilled holes and the comb-shaped branch holes, and then gas extraction is performed on the extraction layer (layer 2 coal seam) after hydraulic fracturing, and the extraction operation is performed on the layer 2 coal seam after the gas extraction reaches the standard. In the mining operation process, the coal seam of the top and bottom plates of the coal seam and the rock stratum are all affected by mining to form a goaf 8, the pressure of the coal seam of the top and bottom plates of the coal seam and the rock stratum can be relieved to generate a fracture zone 9, and the directional long drilling holes and the comb-shaped branch holes which are constructed at the moment can be used for extracting pressure relief gas of an overlying adjacent layer (the 1 st layer of coal seam) and an underlying adjacent layer (the 3 rd layer to the n th layer of coal seam). The method realizes the coordinated and efficient extraction of the gas of the coal seam of the pre-extraction layer (the 2 nd layer of coal seam) and the gas of the pressure relief extraction adjacent layer (the lower adjacent layer and the upper adjacent layer of the 2 nd layer of coal seam).
Example 3: referring to fig. 6, if the nth layer of coal seam is mined first, the final position of the comb-shaped branch holes falls on the bottom plate of the coal seam n at 1m of the rock. And so on, as can be obtained from fig. 6, the coordinated efficient extraction of the gas of the coal bed of the pre-extraction layer (the nth layer of coal bed) and the gas of the adjacent layer (the 1 st layer to the n-1 layer of coal bed) covered by the pressure relief extraction is realized.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.
Claims (3)
1. The method for efficiently extracting the gas of the close-range coal seam group mining layer and the adjacent layer in a coordinated manner is characterized by comprising the following steps of:
s1: arranging directional long drilling holes and comb-shaped branch holes;
the directional long drilling holes are arranged in an upper hard rock stratum of a fracture zone of a top plate of a shallowest part of the coal bed in the same group of close-range coal beds;
s2: calculating the parameters of the directional long drilling and comb-shaped branches Kong Shigong;
the comb-shaped branch hole terminal position is arranged at a rock stratum 1m below the first mining layer bottom plate;
the comb finger Kong Shigong parameters are calculated with the expression:
X n ＝Y n ＝(X 1 2 ÷K n1 ) 0.5 ×K y ÷i 0.5
wherein X is n 、Y n The construction distance and the inclined construction row distance of the comb-shaped branch holes of the nth layer of coal bed are respectively that is the nth layer ofA layer coal seam trend and a fracturing range; x is X 1 K is the hydraulic fracturing range of single coal seam trend n1 The thickness influence coefficient of the comb-shaped branch hole coal bed for the n layers of coal beds; k (K) y Is the rock mass energy consumption coefficient; i is the number of comb-shaped branch holes between the primary hydraulic fracturing sections;
the thickness influence coefficient K of the coal bed of the comb-shaped branch hole n1 The calculation formula of (2) is as follows:
K n1 ＝Z n /Z 1 ＝(X 1 *Y 1 )/(X n *Y n *i)＝X 1 2 /(X n 2 *i)
wherein Z is 1 、Z n The sum of the coal seam thicknesses of the single coal seam, the 1 st layer and the n th layer coal seam is respectively Y 1 Is a single coal seam inclined hydraulic fracturing range;
s3: constructing a directional long drilling hole and a comb-shaped branch hole;
s4: staged hydraulic fracturing of a first production layer and a passing coal layer;
s5: coordinating high-efficiency gas extraction of the mining layer and the adjacent layers;
when mining the shallowest part coal seam of the same group of close-range coal seam groups, realizing the coordination of high-efficiency pre-extraction of mining layer gas and pressure relief extraction of all underlying adjacent layer gas; when the deepest part coal seam of the same group of close-range coal seam groups is mined, the high-efficiency pre-extraction of mining layer gas and the pressure relief extraction of all overlying adjacent layer gas are coordinated; when coal beds between the shallowest part and the deepest part of the same group of close-range coal beds are mined, the efficient pre-extraction of mining layer gas and the pressure relief extraction of all underlying adjacent layers and overlying adjacent layer gas are coordinated.
2. The gas-assisted efficient extraction method according to claim 1, wherein in the step S2, the directional long-drilling-tendency construction pitch is the same as the comb-shaped branch-hole-tendency construction pitch.
3. The gas-assisted efficient extraction method according to claim 1, wherein step S4 specifically comprises: and carrying out hydraulic fracturing on the plurality of comb-shaped branch holes passing through the first mining layer and the coal bed.
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